A serving is the amount of food recommended in consumer education materials such as MyPlate. A portion is the amount of a food you choose to eat at any one time â which may be more or less than a serving. Here are some everyday comparisons to help you figure out your serving sizes. 1  1 teaspoon of margarine is the size of one dice. 2  3 ounces of meat is the size of a deck of cards. 3  1 cup of pasta is the size of a baseball. 4  1Â½ ounces of cheese is the size of four stacked dice.
Oxygen: Specialized nerve cells within the aorta and carotid arteries called peripheral chemoreceptors monitor the oxygen concentration of the blood and feed back on the respiratory centers.
All of these nerve cells send impulses back to the brain. Chemoreceptors can also be found in the brain itself, monitoring pH level and alerting the brain to the presence of chemicals which could indicate a problem.hemoreceptors are specialized nerve cells which are designed to respond to chemical stimuli. The body contains both direct and distant chemoreceptors, all of which play important roles in bodily function and daily life.